The instant invention is concerned with a method of calibrating a volumetric fluid flow sensor of a type having a pole magnet armature in which the direction of reciprocation of the armature is co-linear with the magnetic axis thereof. Such a system is further provided with a magnetic field sensor which is in magnetic communication with said magnetic axis. Changes in the field strength of said magnetic axis in the vicinity of said field sensor are monitored to thereby provide an electrical signal which is proportional to changes in volumetric fluid flow passing through an inlet channel and annularly about the pole magnet armature and to an outlet channel of the system.
The prior art includes U.S. Pat. No. 3,759,099 (1973) to McGregor, entitled Flow Meter; and U.S. Pat. No. 4,507,976 (1975) to Banko, entitled Flow Meter with Hall Effect Sensor and Method. However these, and other art known to the inventor, do not involve the use of a magnetic field sensor to measure changes in magnetic flux density of the magnetic axis of the magnetic armature in combination with the control of certain other system variables, these variables including the cross-section of a fluid interface between the fluid inlet channel and fluid outlet channel, modification of the cross-sectional geometry of one or more portions of the path of fluid flow from said inlet to said outlet channel; modification of the geometry, mass or magnetic flux characteristic of the pole magnet armature; or change in the axial location, relative to the axis of the pole magnet armature, of a calibration magnet. Change of any of the variables will affect the actuating characteristic of the armature and thereby of the sensor system.
While my above referenced co-pending application is directed to a selective modification and control of the cross-section or fluid interface between the inlet channel and fluid outlet channel, the present invention enlarges upon said method by setting forth a method by which other system variables of the volumetric fluid flow sensor may be modified to effect desired changes in the actuating characteristic, that is, of the available flux lines that will be monitored by said magnetic field sensor.
The underlying importance of the present method resides in the provision of an efficient and economical method for effecting changes in ranges of volumetric fluid flow measurements which, heretofore, could only be achieved through the use of more complex equipment and more time consuming methods, both involving substantially greater cost than is the case in fluid flow sensors embodying the inventive method described herein.